Method for recovering sulphur from waste liquors containing sulphidic sodium compounds



Patented Jan. 13, 1942 UNITED STAT TENT OFFICE METHOD FOR RECOVERING SULPHUR FROM WASTE LIQUORS CONTAINING SULPHIDIC SODIUM COMPOUNDS Johann Joseph Stoeckly, Teltow, and Elmar Profit, Berlin-Lichterfelde, Germany, assignors to North American Rayon Corporation, New York, N. Y., a corporation of Delaware No Drawing. .Application September 15, 1939, Serial No. 295,158. In Germany September 29,

2 Claims.

are treated with 25 grams of sodium sulphate per liter, whereupon so much sulphuric acid is added until a distinctly acid reaction is produced. The decomposition of the sodium compounds serves to raise the total content of sodium sulphate to the desired amount. The hydrogen sulphide set free dissolves in the liquid, the total volume thereof being sufiicient to hold the hydrogen sulphide in solution for a time. Sulphur dioxide is then The recovery of sulphur from waste industrial passed in until the dissolved hydrogen sulphide is liquors containing sulphides of sodium, especialdecomposed. This stage is evidenced by the ly from desulphurizing baths and the like, of fact that the solution smells faintly of sulphur the type resulting from the manufacture of visdioxide. Next, the sulphuric acid content is supcose artificial silk and which contain decompoplemented until 20 grams of sulphuric acid per sition products of cellulose, is a difficult matter, liter can be determined by titration. Finally the largely because the sulphur when precipitated entire mass of liquid is heated to 80 C. and then from the sulphidic compounds by prior art allowed to stand for 15 hours during which time methods is obtained in such finely colloidal condithe liquid is allowed to cool down. The greater tion that it is hardly possible to make it settle portion of the suspended material settles out. out within any commercially economical space The supernatant liquid is siphoned off from the of time or even to remove it by filtration. The sulphur slurry and filtered. cellulose decomposition products such as hemi- Exam [8 2 cellulose and even glucose act as protective 001- p l i in t case The same type of sulphidic liquor described It is an object of the present invention to conunder ple 1 is treated at 70 C. by passing vert the sulphur of colloidal sulphur suspensions therethrough until a p When c fie constituting such liquors into a form that is ameno longer evolves hydro en s p Therm-113011 nable to settling and filtration. To this end the the Solution is treated With 5 ams of sodium method consists in causing the liquors to have an sulphate p liter a u s y a fi d with appreciable sodium sulphate concentration Sulphuric d until 20 grams o Su ph r c ac d amounting to at least to grams of sodium P liter n be determined y ti ration. The sulphate per liter and a, sulphuric acid concen- 50111131011 is then heated t0 80 and allowed 130 tration ranging from 15 to 25 grams (preferably Stand for 15 1101115 during which e it s about 20 grams) of sulphuric acid per liter, lowed to cool down. The greater portion of the thereupon warming the solutions and then allow- 35 Sulphur Settles The Supernatant liquid is ing them to stand for a number of hours while p d the S p u S u ry which contains cooling, e. g. for 10 to 20 hours. A large portion hemicellulose is worked up separately and the of the sulphur settles out during this period. s uti which s w ys s m w at tur d, is The solution which is siphoned off, if not clear, filteredmay be eparated from th r id ulphur i 40 Modifications of this invention will readily be suitable known manner by filtration. To illusecognized by t s Skilled in the and it s trate the invention, several non-limiting emintended to cover all modifications coming within bodimental examples of its application are given the scope of the appended claims. below What is claimed is:

Example 1 1. The method of recovering sulphur from Waste bath liquors from the viscose artificial g t i i 32 agilficlal i dustry containing sulphur and having, for y w p 585 a ng mm su i e a $11k m sulphunc acld to a waste liquor containing soexample the followmg compost dium sulphides and cellulose decomposition prod- Grams per liter 50 ucts to form colloidal sulphur therein, raising the Free NaOH .1 sodium sulphate content of said liquor to 35 to Na2CO3 2- 40 grams per liter and the sulphuric acid con- NazSzOs 1. tent thereof to 15 to 25 grams per liter, heating Sodium sulphides 3.5 said liquor to a temperature of about 80 C. and Hemicellulose 5- then while cooling allowing the liquor to stand to precipitate the sulphur contained therein in a condition amenable to rapid settling and filtration.

2. The method of recovering sulphur from waste liquors of the viscose artificial silk industry which comprises adding sodium sulphate and sulphuric acid to a waste liquor containing sodium sulphides and cellulose decomposition products to form colloidal sulphur therein, raising the sodium sulphate content of said liquor to 35 to 40 grams per liter and the sulphuric acid content thereof to 20 grams per liter, heating said liquor to a temperature of about 80 C. and then While cooling allowing the liquor to stand to precipitate the sulphur contained therein in a condition amenable to rapid settling and filtration.

J OI-IANN JOSEPH STOECKLY. ELMAR PROFFT. 

